The present invention relates to a disk drive, such as a magnetic disk drive. In particular, the present invention relates to an air stripper configured for use in the disk drive to reduce synchronous spindle error.
In one typical disk drive, a plurality of disks are secured to a spindle for co-rotation about a central axis. A spindle motor is connected to the spindle for causing rotation of the spindle and the attached disks. The plurality of disks are known as a disk pack. Each disk in the pack includes first and second generally planar recording surfaces. The recording surfaces have a plurality of generally concentric data tracks between an outer disk diameter and an inner disk diameter.
An actuator arm assembly is positioned adjacent the disk pack and includes a plurality of head arms which extend between the disks for actuation across the data tracks. The head arms are movable between an outer position and an inner position, the inner position being closer to the central axis than the outer position. The head arms support an air bearing disk head slider proximate each recording surface for reading from and writing to the data tracks. As the disk rotates, it pulls air between the disk surface and the slider which produces positive pressure on the slider causing it to lift and to fly several microinches above the disk surface.
In large storage systems, several disk drives are connected together to form a storage device having a larger memory capacity and faster read and write cycle rates. For example, eight individual disk drives may be connected together in parallel such that each bit of an eight bit word is written to a separate disk drive. Therefore, an eight bit word may be written in the same period of time as a single bit. Each drive, however, must be synchronized so that each disk pack rotates at exactly the same velocity as the other disk packs. Otherwise, information stored on the disks may be lost.
Each recording surface includes an index position on the data tracks which lies generally on a radial axis of the disk. The index position provides a reference point or mark among individual bit positions on the data tracks. The storage system generates a sync signal that is applied to each drive in the system to synchronize rotation of each disk pack. If the disk packs are not synchronized, one or more bits of the eight bit word may be written to the wrong location or bit position on a particular data track with respect to the index. As a result, this information may be unrecoverable.
Index leading occurs when one disk pack rotates faster than the other disk packs. Index lagging occurs when one disk pack rotates slower than the other disk packs. Variation between rotational velocities of disk packs is known as synchronous spindle error. A disk drive that is capable of maintaining a constant rotational velocity for reducing synchronous spindle error is desired.
Constant rotational velocity is also a critical for maintaining a constant slider flying height. When the rotational velocity increases, the positive pressure beneath the air bearing surface also increases causing the slider to fly at a greater distance from the disk surface. Resolution between individual bit positions on the disk surface is therefore reduced. When the rotational velocity decreases, the positive pressure beneath the air bearing surface also decreases causing the slider to fly closer the disk surface, which increases the risk of a head crash.
Air strippers have been used in magnetic disk drives to improve air filtration. The air strippers include a plurality of stripping members which extend into a volume of air that exists between adjacent disks in the disk pack. The stripping members are oriented generally parallel to the direction of air flow for stripping the air between the disks and directing the air into an air filter. This orientation minimizes power consumption of the spindle motor which is increased by insertion of the air stripper into the air flow. The air strippers have also been used to lessen the windage affects seen by the magnetic disk head sliders.